Hardpan n. : The hard substratum. Same as Hard pan, under Hard, a.

Example:


Taxonomy
the Hardpan, soil, clay particles, free encyclopedia, soil particles, deposits, hardpans, matrices, gypsum, hard pan, mineral salts, soil amendments, soil layer, soil structure, soil pH, proper drainage, search, ouklip.

Defination from the web:
hardpan or ouklip is a general term for a dense layer of soil, usually found below the uppermost ... Others are man-made, such as hardpan formed by compaction from repeated plowing particularly with moldboard plows and /or heavy traffic and ...